The second leaders' debate had a live audience of 4.1 million viewers across Sky News, BBC News Channel and Sky3 last night, Thursday 22 April – a huge audience for digital television.

Gordon Brown, David Cameron and Nick Clegg's second televised encounter attracted 2.125 million viewers, an 8.7% audience share, between 8pm and 9.30pm on Sky News, which hosted the debate in Bristol with Adam Boulton.

Simulcasts on BBC News Channel (1.362 million/5.6%) and Sky3 (586,000/2.4%) took the total live audience to 4.073 million (16.7%).

A further 310,000 (6.6%) watched BBC2's repeat of the debate between 11.30pm and 1am.

Last Thursday's first leaders' debate attracted a live audience of 9.4 million viewers (37%) on ITV1 between 8.30pm and 10pm.

The second leaders' debate was the most watched programme ever on Sky News, which launched in 1989.

Overall reach – viewers who tuned in for at least three consecutive minutes – across the three channels was 6.5 million. Sky News' daily three-minute reach, 5.4 million, was its best since the 2003 Iraq war.

John Ryley, Head of Sky News, said: "It is clear that the Leaders' Debates have struck a chord with the British public and energised the election campaign, just as we hoped they would when we called on the three main party leaders to join in a televised debate. I am delighted that so many people chose to watch Sky News' coverage on all of the platforms where it was available."

The 15-minute peak came between 9pm and 9.15pm, with 4.592 million (18.8%) across the three channels. Sky News had its biggest ever peak audience during this period, with 3.355 million – the previous high was 1.7 million during the Louise Woodward trial in October 1997.

Sky News, BBC News Channel and Sky3 all enjoyed a huge upsurge in their ratings during the debate compared with normal viewing levels.

For Sky News, the average audience between 8.pm and 9.30pm over the past three months was 42,000 viewers, while the equivalent figure for the BBC News Channel is 88,000.

The fact that the debate was only available on digital TV and was not simulcast on any of the five main terrestrial networks – particularly one of the BBC channels – attracted criticism. However, about 95% of UK TV homes now have access to digital TV.

BBC Radio 4 also simulcast the debate, but radio audience research body Rajar only publishes figures every three months – and then ratings for individual shows are not broken out.